Mg-Si-Sn基热电发电器件中电极材料的设计、制备与表征

发布时间：2018-03-28 02:09

本文选题：Mg-Si-Sn单臂　切入点：多层电极　出处：《武汉理工大学》2015年硕士论文

【摘要】：Mg-Si-Sn热电材料是重要的中温热电材料体系,在工业余热和汽车尾气回收发电领域具有广阔应用前景。关于Mg-Si-Sn器件的研究甚少,本论文以Mg2.16(Si0.3Sn0.7)0.98Sb0.02热电单臂为研究对象,设计了一种与该热电材料匹配的多层电极,优化了多层电极的连接工艺;对Mg2.16(Si0.3Sn0.7)0.98Sb0.02热电材料与多层电极的连接状态进行了表征,包括界面微观结构、化学成分、接触电阻、剪切强度以及高温稳定性;在此基础上组装了n型Mg-Si-Sn/p型Cu2Se热电单偶,测试了热电单偶的热电转换效率和输出功率,对焊接界面的高温稳定性进行了研究,其主要工作的结果如下:n型Mg2.16(Si0.3Sn0.7)0.98Sb0.02热电材料的多层电极满足器件设计要求,该多层电极由第一Ni-Al合金层/第二Ni-Al合金层/Ag构成,第一Ni-Al合金层热膨胀系数可与Mg2.16(Si0.3Sn0.7)0.98Sb0.02热电材料良好匹配,Ag层焊接性能良好;多层电极与热电材料的结合界面良好,无明显微裂纹,其无明显元素互扩散;界面接触电阻介于0.07~0.13 m?之间,占热电材料内阻的3.5~8.3%,多层电极与热电材料的剪切强度高于热电材料自身强度。n型Mg2.16(Si0.3Sn0.7)0.98Sb0.02热电材料/多层电极在573 K、673 K和773 K下分别退火一周热稳定性研究表明:当退火温度在673 K及以上时,多层电极第一Ni-Al合金层会由Al,NiAl3,Ni2Al3和Ni多相组成转变为Al和NiAl3两相稳定结构,热电材料/多层电极界面孔隙逐渐增多,Mg向多层电极中的扩散加剧,热电材料/多层电极的接触电阻由退火前的0.10 m?增加到773 K退火后的0.21m?。n型Mg2.16(Si0.3Sn0.7)0.98Sb0.02热电材料/多层电极在773 K下退火不同时间的热稳定性研究表明:当退火时间达到27 h时,多层电极的第一Ni-Al合金层物相得到稳定结构,多层电极的第一Ni-Al合金层内部及热电材料/多层电极结合界面产生大量孔洞,这些孔洞分布于相界面处,Mg在多层电极的第一Ni-Al合金层中含量逐渐增大;接触电阻由退火前的0.12 m?增大到0.16 m?,其增幅为33%。低温Pb-Sn焊接可以成功组装n型Mg-Si-Sn/p型Cu2Se热电单偶。采用4点探针法对n型Mg-Si-Sn/p型Cu2Se热电单偶的电连接性能进行检测,得到用于热电装换效率测试的样品。该单偶的热电转换性能测试结果表明:在ΔT=410 K时,转化效率达到峰值6.33%;而在ΔT=477 K时,输出功率达到最大值264.39 mW。n型Mg-Si-Sn单臂与导流铜片焊接头在773 K下退火1 d、2 d和5 d热稳定性研究表明:Pb-Sn焊料在退火1 d后挥发,随着退火时间延长,焊接界面会紧密融合,Sn向焊接界面侧发生扩散。p型Cu2Se单臂与导流铜片焊接头在773 K下退火1 d和2 d热稳定性研究表明:随着退火时间延长,电极侧Ni和导流片Cu会向焊料层扩散,形成Ni-Pb-Sn-Cu合金,该合金在773 K下稳定存在,同时焊料层中产生大量孔洞,随后发展为缝隙,造成焊接界面的脱离。
[Abstract]:Mg-Si-Sn thermoelectric material is an important medium temperature thermoelectric material system, which has a broad application prospect in the field of industrial waste heat and automobile exhaust recovery power generation. There are few researches on Mg-Si-Sn devices. In this paper, Mg2.16(Si0.3Sn0.7)0.98Sb0.02 thermoelectric single arm is the research object. A multilayer electrode matched with the thermoelectric material was designed, and the connection process of the multilayer electrode was optimized, and the connection state between the Mg2.16(Si0.3Sn0.7)0.98Sb0.02 thermoelectric material and the multilayer electrode was characterized, including interface microstructure, chemical composition, contact resistance. Based on the shear strength and high temperature stability, n-type Mg-Si-Sn/p Cu2Se thermoelectric single couple was assembled, the thermoelectric conversion efficiency and output power of the thermoelectric single pair were tested, and the high temperature stability of the welding interface was studied. The main results of this work are as follows: the multilayer electrode of the Mg2.16(Si0.3Sn0.7)0.98Sb0.02 thermoelectric material of type 1: n meets the design requirements of the device. The multilayer electrode is composed of the first Ni-Al alloy layer / the second Ni-Al alloy layer / Ag. The thermal expansion coefficient of the first Ni-Al alloy layer can match well with the Mg2.16(Si0.3Sn0.7)0.98Sb0.02 thermoelectric material, the bonding interface between the multilayer electrode and the thermoelectric material is good, there is no obvious microcrack, and there is no obvious element interdiffusion, and the interface contact resistance is between 0.07 and 0.13 m? Between, The shear strength of multilayer electrode and thermoelectric material is higher than that of thermoelectric material. N type Mg2.16(Si0.3Sn0.7)0.98Sb0.02 thermoelectric material / multilayer electrode annealed at 573K 673K and 773K respectively. When the fire temperature is 673 K and above, The first Ni-Al alloy layer of multilayer electrode will change from Al Ni Al 3N Ni 2AL 3 and Ni multiphase to Al and NiAl3 two phase stable structure, the interface pore of thermoelectric material / multilayer electrode will increase gradually and the diffusion of mg to multilayer electrode will be intensified. The contact resistance of thermoelectric material / multilayer electrode is 0.10 m? Increased to 0.21m? after annealing at 773K? The thermal stability of n type Mg2.16(Si0.3Sn0.7)0.98Sb0.02 thermoelectric material / multilayer electrode annealed at 773K for different time shows that the first Ni-Al alloy layer phase of the multilayer electrode is stable when annealing time is up to 27 h. In the first Ni-Al alloy layer of multilayer electrode and the interface of thermoelectric material / multilayer electrode, a large number of pores were produced, and the content of mg in the first Ni-Al alloy layer of multilayer electrode gradually increased, and the contact resistance was increased from 0.12 m? Increase to 0.16 m? Low temperature Pb-Sn welding can successfully assemble n type Mg-Si-Sn/p Cu2Se thermoelectric single pair. The electrical connection performance of n type Mg-Si-Sn/p Cu2Se thermoelectric single pair is tested by 4 point probe method. The results show that the conversion efficiency reaches a peak value of 6.33 at 螖 T _ (10) K, while at 螖 T _ (477) K, the conversion efficiency reaches a peak value of 6.33 at 螖 T _ (410K), while at 螖 T _ (477) K, the conversion efficiency reaches a peak value of 6.33. Thermal stability of 264.39 mW.n type Mg-Si-Sn single arm welding joint annealed at 773K for 1 d and 5 d the thermal stability of the 1: Pb-Sn solder evaporated after 1 day annealing and with the increase of annealing time. The thermal stability of welding joints annealed at 773K for 1 d and 2 days after annealing at 773K shows that the thermal stability increases with the increase of annealing time. On the electrode side, Ni and Cu can diffuse to the solder layer to form Ni-Pb-Sn-Cu alloy. The alloy exists stably at 773K, at the same time, a large number of holes are produced in the solder layer, and then it develops into a gap, which results in the breakaway of the welding interface.
【学位授予单位】：武汉理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB34

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